1. Field of the Invention
The present invention relates to a semiconductor device, a transmission system, a method for manufacturing a semiconductor device, and a method for manufacturing a transmission system that allow high-speed data transmission by use of an electrical signal having a millimeter-wave frequency.
2. Description of the Related Art
In recent years, demands for high-speed data transmission for transmitting large-volume data such as moving image data at high speed are increasing. For such high-speed data transmission, there is a method of using an electrical signal having a millimeter-wave frequency as one of high-frequency signals.
For example, an oscillating circuit in which a resonant electrode is formed in a resonator is disclosed in PCT Patent Publication No. WO2006/33204 (FIG. 1 and FIG. 8, hereinafter Patent Document 1). In this oscillating circuit, the resonant electrode is formed in the resonator and the resonator and a transmission line provided on a circuit board are connected to each other by a bonding wire. By this resonator, a resonant frequency in the range of 22 GHz to 26 GHz can be achieved.
FIG. 23 is a perspective view showing a configuration example of a semiconductor device 100 of a related art. FIG. 24 is a plan view showing a configuration example of a major part of the semiconductor device 100, and FIG. 25 is a front view thereof. As shown in FIGS. 23 to 25, the semiconductor device 100 includes a circuit board 10 serving as a semiconductor circuit element that processes an electrical signal having a millimeter-wave frequency, and an interposer substrate (hereinafter, referred to as the substrate 17) having a transmission line 14 that transmits the electrical signal processed by the circuit board 10.
The circuit board 10 has a terminal unit 11 composed of a signal transmission terminal 11a and grounding terminals 11b. The substrate 17 has a terminal unit 13 composed of a signal transmission terminal 13a and grounding terminals 13b. The signal transmission terminal 11a is connected to the signal transmission terminal 13a via a wire 12a included in a wire unit 12. The grounding terminals 11b are connected to the grounding terminals 13b via wires 12b included in the wire unit 12.
The substrate 17 has a first dielectric layer (hereinafter, referred to as the dielectric layer 17a), a grounding layer 17b, and a second dielectric layer (hereinafter, referred to as the dielectric layer 17c). The grounding layer 17b is formed of copper or aluminum and has a function for grounding. Vias 19 having electrical conductivity are provided in the dielectric layer 17a at the positions on which the grounding terminals 13b are provided. The semiconductor device 100 is grounded by electrical connection between the grounding terminals 13b and the grounding layer 17b through the vias 19. The dielectric layer 17a has a predetermined dielectric constant. The dielectric layer 17a, the transmission line 14, and the grounding layer 17b form a micro-strip line. The dielectric layer 17c has a function to support the dielectric layer 17a and the grounding layer 17b. 
The transmission line 14 is connected to the signal transmission terminal 13a, and this transmission line 14 transmits a millimeter-wave electrical signal in a predetermined direction (in FIGS. 24 and 25, in the right direction). An antenna part 16 is connected to the transmission line 14, and the antenna part 16 converts the millimeter-wave electrical signal to an electromagnetic wave signal. The semiconductor device 100 is sealed by a sealing resin 18 in such a way that an upper part of the substrate 17 is covered.
The millimeter-wave electrical signal resulting from signal processing by the circuit board 10 is transmitted by the transmission line 14 on the substrate 17 via the wire 12a. The transmitted millimeter-wave electrical signal is changed to the electromagnetic wave signal by the antenna part 16, and the electromagnetic wave signal passes through the sealing resin 18 to be output to the external.
A simulation result relating to the millimeter-wave signal transmission by the semiconductor device 100 will be described below. FIG. 26 is a graph showing a characteristic example of the semiconductor device 100, obtained by the simulation. As shown in FIG. 26, this simulation result is represented by plotting the frequency (GHz) of the millimeter-wave electrical signal on the abscissa and plotting the S-parameter magnitude (dB) on the ordinate, and is obtained by calculation with use of the semiconductor device 100 shown in FIGS. 23 to 25 based on parameters shown in Table 1. The S-parameter magnitudes refer to the parameter magnitudes representing the transfer and reflection of the millimeter-wave electrical signal. The full lines in FIG. 26 indicate transfer characteristics S12 and S21, and the dashed lines indicate reflection characteristics S11 and S22.
TABLE 1Thickness A1 of transmission line 1418μmWidth A2 of transmission line 14130μmLength A3 of transmission line 142mmThickness A5 of dielectric layer 17a70μmRelative dielectric constant of dielectric layer 17a4.7 Dissipation factor of dielectric layer 17a0.02Relative dielectric constant of sealing resin 184.2 Dissipation factor of sealing resin 180.02Length of wire 12a635μmLength of wire 12b711μm
As shown in Table 1, in this simulation, the width A2 and the length A3 of the transmission line 14, shown in FIG. 24, are set to 130 μm and 2 mm, respectively. Referring to FIG. 25, the thickness A1 of the transmission line 14 is set to 18 μm, and the thickness A5 of the dielectric layer 17a in the substrate 17 is set to 70 μm. Furthermore, the relative dielectric constant and the dissipation factor of the dielectric layer 17a are set to 4.7 and 0.02, respectively. The relative dielectric constant and the dissipation factor of the sealing resin 18 are set to 4.2 and 0.02, respectively. The lengths of the wire 12a and the wire 12b are set to 635 μm and 711 μm, respectively.
According to this simulation result, the S-parameter magnitudes of the transfer characteristics S12 and S21 are lower than those of the reflection characteristics S11 and S22 over the frequency range of the millimeter-wave electrical signal from 40 GHz to 80 GHz. This indicates that the data transmission is difficult when the frequency of the millimeter-wave electrical signal is in the frequency band from 40 GHz to 80 GHz.